Regular FMP13 can act as a host, but for no more than 5 clients, and it is not true server software (does not run as a service, has no live backups,...)
FileMaker Server 13 is recommended instead. Ideally you do not want to put FMS on a server that does other things, especially file sharing. FMS has its own networking protocol so users should not try to open files through a network share.
Then, we can use FM server to share Word files and photos?
You can, but it is not best practice, it adds a bit of risk for instance. One configuration mistake on the OS-level network sharing to show the folders with Word files and photos may accidentally expose your live FM files or backups.
And if the server machine is not up to the task, it may affect performance.